Note that some extension create special opt-out cookies that you can't remove as long as the extension is installed. Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem. *Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance *Do NOT click the Reset button on the Safe Mode start window *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes ---- If clearing cookies didn't help then it is possible that the cookies.sqlite file that stores the cookies got corrupted. *Rename (or delete) <b>cookies.sqlite</b> (cookies.sqlite.old) and delete other present cookies files like <b>cookies.sqlite-journal</b> in the Firefox profile folder in case the file cookies.sqlite got corrupted. *http://kb.mozillazine.org/Cookies *https://support.mozilla.org/kb/Deleting+cookies You can use this button to go to the currently used Firefox profile folder: *Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder) *http://kb.mozillazine.org/Profile_folder_-_Firefox

Type '''about:preferences#privacy'''<enter> in the address bar. Next to '''History,''' choose '''Use Custom Settings''' Near the bottom, turn on '''Clear History When Firefox Closes''' Then to its far right, press the '''Settings''' button.